Stone tool knapping quality and raw material selection behaviour in the Inner Asian Mountain Corridor

Stone tool knapping quality is an important parameter in the study of lithic technology. A number of experimental and objective studies have contributed to the discussion on how stone quality affects the knappability and the final shape of an end product. However, systematic studies on how stone mechanical properties affect knappability and raw material selection behaviour remain few. Here, we investigate geological and archaeological samples of porphyry, chert, and sandstone from the Palaeolithic sites of southern Kazakhstan to evaluate whether the acquisition of raw materials was driven by specific mechanical properties (e.g., ease of knapping). We tested their degree of knappability using the Vickers indentation method and four-point bending tests. Our results suggest high variability in the mechanical properties of the studied samples. Porphyry and chert demonstrate unexpectedly high values of force to initiate a knapping crack and low fracture predictability. Despite such knapping force requirements, these raw materials were preferred by their knappers, suggesting that raw material selection was governed by other criteria, such as resistance to abrasion and edge damage.